[acarter5251]

I have come across a paper in the literature where an oxazolidinone ring is formed and then reacted with a primary amine to form a urea.  However, in the paper, they mention that the reaction does not occur with 2-oxazolidinone and a primary amine.  I have included this reaction below.

My question is, why does this occur in the molecule that was being worked with, but not with the more simplified case of 2-oxazolidinone?  It seems obvious that it must have something to do with the rest of the structure that this functionality is incorporated into, but I'm just not seeing why and was looking for some guidance.

[acarter5251]

Looking at a simplified case, it appears that it may be due to the ring strain of the bicyclic oxazolidinone.  I looked at some 3D models, and while the oxazolidinone by itself is relatively flat, the bicyclic compound has a bit of a pucker with a torsion angle of about 36 degrees between the C-N and C-O bonds.  Does this make sense with what I am seeing with the reaction occurring in the bicyclic system but not in 2-oxazolidinone?